Others are so young, that September 11th is not even a memory for them - so young that they can't even begin to understand what it did to us.

"It's difficult. It's a difficult conversation to have, but you know, it's a good one to have, and that's certainly why we're here today," says Sean Latimer.

What unites all of the different people who visit the 9/11 Memorial is the pain that still pierces our hearts, and the sorrow that comes with that day 15 years ago that changed our lives forever.

To honor those who rushed into danger when others ran the other way, a solemn memorial service was held at St. Patrick's Cathedral.

343 firefighters died in the September 11th terrorist attacks. Firefighters who carried the wounded on their backs, and carried a city and a nation when we had trouble standing.

"The horror, the sense that we were dealing with something that we have never seen before, and we relive it this time of year - it comes back in waves," said Mayor Bill de Blasio.

The courage and the honor of those fallen heroes are found in the daughters of Battalion Chief Joseph Grislack - living reminders of the burden we bear, and the hope that gives us the strength to move foreward.

With Sunday being such an important day, there were so many who Eyewitness News spoke to who said they came Saturday to not only try to get a little more of a private moment, but also give those families on Sunday a little more time to grieve.